Hormone of insects

Esterases of the Juvenile Hormone of Insects Many works have been dedicated to the inhibition of esterases of the juvenile hormone of insects. The purpose of these works is to control insect populations by ehminating their metamorphosis. Among the numerous trifluoromethyl ketones that have been synthesized, thioalkyl derivatives of trifluoroacetone have been shown to be the most active ones. Curiously, the corresponding alcohols are also excellent inhibitors. Trifluoromethyl ketones can also inhibit other insect esterases antenna esterases and esterases that are involved in the release of pheromones (Figure 7.33). The inhibition of these latter ones can also be interesting for insect control purposes. 

Hormones of insects and crustaceans. Peptide neurohormones of insect brains348 include the pentapeptide proctolin (Table 30-5), which was first iso-lated from the cockroach and has since been found in crustaceans and in mammalian brain. It has been traced to specific insect neurons.349 A nonapeptide neurohormone from the shore crab does not resemble any other known vertebrate or invertebrate hormone.350... 

Developments in the chemistry of hormones of insects and other arthropods have shown that the simple picture of a few compounds and a few actions has become less simple. Advances in analytical methods and the increasing number of species studied have thrown up more variations on the simple rules. We are learning more about the interactions between plants and insects, and the conservation of biosynthetic routes between them, and across the phyla. The subject of eicosanoids in insects and lower animals is going to demand further investigation. 

Phvtoluvenolds. Wigglesworth (JL) demonstrated that a hormone secreted by the insect corpora allata was responsible for the control of differentiation in immature insects and reproduction in adult female insects. Williams (3) prepared an active extract of this hormone from adult male cecropia moths and called it "juvenile hormone". We were able to derive sufficient knowledge of the chemistry of the juvenile hormone from the study of the active cecropia extract to synthesize JH III Q). Seven years later its presence as a natural hormone in the tobacco hornworm was confirmed Ci). Three other analogous juvenile hormones (JH 0, I, II) have been found to occur only in lepidoptera (5, ., 2.) (Figure 1). Juvenile hormone III is the principal juvenile hormone of insects and has been demonstrated in all of the insect taxa investigated. 

Interestingly, the leaves of seme trees, such as hemlock, make a chemical similar to the juvenile hormones of insects. When larvae (caterpillars) feed on these leaves, they cannot metamorphose into the adult form. Aj arently, this is a chemical defense mechanian seme trees use to prevent leaf-feeding insects from reaching sexual maturity. 

As in insects, a complex interaction of hormones in the amphibian larva precipitates metamorphosis. Ultimately, two major classes of hormones act together to control amphibian metamorphosis the thyroid hormones (made by the thyroid gland) and prolactin (made by the pituitary gland). Thyroid hormones function somewhat like the molting hormones of insects, in that an increase of their concentration relative to prolactin leads to metamorphosis of the larva into the adult. Prolactin functions somewhat like the juvenile hormones of insects, in that it tempers the action of the thyroid hormones. In most species, thyroid hormones increase dramatically in concentration during metamorphosis and this stimulates resorption of certain larval organs and differentiation of new adult organs. 

Ecdysteroids are the steroid hormones of insects, where they regulate moulding and metamorphosis. As ecdysteroids are essential to the normal development of insects, it was presumed that some plant secondary metabolites might have the ecdysteroid antagonistic activity and be capable of affecting insect development. Such compounds would be useful... 

Hom DHS, Middleton EJ, Wunderlich JA, Hampshire F (1966) Identity of the moulting hormones of insects and crustaceans. Chem Commun 1966 339-340... 

Epoxidation of the following compound in a laboratory synthesis gives a 40% yield of the juvenile hormone of insects. Explain why only a 40% yield is obtained. 

Hormones are found even among invertebrates. We will single out the hormones of insects from this rather comprehensive area, because they have been investigated most thoroughly. 

The hormone that inhibits molting is methyl famesoate, which is very similar to the juvenile hormone of insects it inhibits the functioning of the Y organ between two successive molts. In insects this second hormone is... 

The first moulting hormone of insects and crustaceans, a-ecdysone (806), was isolated by Butenandt and Karlson 445) in 1954. Early studies on these compounds which are called ecdysones because they... 

Takemoto, T., S. Ogawa, and N. Nishimoto Isolation of the Moulting Hormones of Insects from Achyranthis Radix. J. Pharmac. Soc. Japan 87, 325 (1967). 

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